Emit a whole line in one go

Since the graph prefix will be printed when calling
emit_line, so the functions should be used to emit a
complete line out once a time. No one should call
emit_line to just output some strings instead of a
complete line.
Use a strbuf to compose the whole line, and then
call emit_line to output it once.

Signed-off-by: Bo Yang <struggleyb.nku@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff.c

@@ -370,6 +370,9 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 	static const char atat[2] = { '@', '@' };
 	const char *cp, *ep;
+	struct strbuf msgbuf = STRBUF_INIT;
+	int org_len = len;
+	int i = 1;
 
 	/*
 	 * As a hunk header must begin with "@@ -<old>, +<new> @@",
@@ -384,17 +387,36 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
 	ep += 2; /* skip over @@ */
 
 	/* The hunk header in fraginfo color */
-	emit_line(ecbdata->opt, frag, reset, line, ep - line);
+	strbuf_add(&msgbuf, frag, strlen(frag));
+	strbuf_add(&msgbuf, line, ep - line);
+	strbuf_add(&msgbuf, reset, strlen(reset));
+
+	/*
+	 * trailing "\r\n"
+	 */
+	for ( ; i < 3; i++)
+		if (line[len - i] == '\r' || line[len - i] == '\n')
+			len--;
 
 	/* blank before the func header */
 	for (cp = ep; ep - line < len; ep++)
 		if (*ep != ' ' && *ep != '\t')
 			break;
-	if (ep != cp)
-		emit_line(ecbdata->opt, plain, reset, cp, ep - cp);
+	if (ep != cp) {
+		strbuf_add(&msgbuf, plain, strlen(plain));
+		strbuf_add(&msgbuf, cp, ep - cp);
+		strbuf_add(&msgbuf, reset, strlen(reset));
+	}
+
+	if (ep < line + len) {
+		strbuf_add(&msgbuf, func, strlen(func));
+		strbuf_add(&msgbuf, ep, line + len - ep);
+		strbuf_add(&msgbuf, reset, strlen(reset));
+	}
 
-	if (ep < line + len)
-		emit_line(ecbdata->opt, func, reset, ep, line + len - ep);
+	strbuf_add(&msgbuf, line + len, org_len - len);
+	emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
+	strbuf_release(&msgbuf);
 }
 
 static struct diff_tempfile *claim_diff_tempfile(void) {